Visceral Adipose Tissue Inflammation Research Articles

Transcriptional and hormonal control of adipose Treg heterogeneity and function.

Adipose tissue stores excess energy and produces a broad range of factors that regulate multiple physiological processes including systemic energy homeostasis. Visceral adipose tissue (VAT) plays a particularly important role in glucose metabolism as its endocrine function underpins food uptake and energy expenditure. Caloric excess triggers VAT inflammation which can impair insulin sensitivity and cause metabolic deregulation. Regulatory T cells (Tregs) that reside in the VAT suppress inflammation and protect from metabolic disease. The cellular components of VAT and its secretory products play a vital role in fostering the differentiation and maintenance of VAT Tregs. Critically, the physiology and inflammatory tone of VAT exhibit sex-specific disparities, resulting in substantial VAT Treg heterogeneity. Indeed, cytokines and sex hormones promote the differentiation of distinct populations of mature VAT Tregs, each characterized by unique phenotypes, homeostatic requirements, and functions. This review focuses on key findings that have significantly advanced our understanding of VAT Treg biology and the current state of the field, while also discussing open questions that require further exploration.

Endothelin A Receptor Activation on Vascular Smooth Muscle Cells Mediates Visceral Adipose Tissue Inflammation in an Obese Mouse Model

Obesity causes a pro-inflammatory shift in visceral adipose tissue immune cells that is thought to promote adipocyte dysfunction and obesity pathophysiology. Endothelin-1 (ET-1) is a small peptide produced mostly by endothelial cells that causes inflammation in diseases including a number of nephropathies and autoimmune diseases. ET-1 is increased in obese patients and in rodent models of obesity. Our lab has demonstrated that mice fed high fat diet (HFD) have an increase in visceral adipose tissue CD4+ and CD8+ T cells and a reduction in anti-inflammatory eosinophils that is attenuated by treatment with an ET-1 type A receptor (ETAR) antagonist; however, the mechanisms by which ET-1 leads to inflammation remain unknown. The ETAR is highly abundant on vascular smooth muscle cells (VSMC), where activation causes a significant increase in pro-inflammatory interleukin-6 production. We hypothesized that elevated ET-1 production in visceral adipose causes a pro-inflammatory shift in tissue immune cells by activating VSMC ETAR. To test this hypothesis, 8-week-old floxed control and vascular smooth muscle cell-specific ETA knockout (SMAKO) mice were placed on either normal (n=5 and 3 for control and SMAKO respectively) or high-fat diet (n=6 and 4 for control and SMAKO respectively) for 12 weeks. Tissue immune cells were quantified by flow cytometry. As expected, HFD fed mice had significantly increased body weight, lean mass, and fat mass, as measured by EchoMRI, compared to NMD fed mice; however, there was no detectable difference due to genotype. There was a significant increase in CD4+ T cells (control NMD: 2.45 ± 0.28 vs. control HFD: 4.37 ± 0.80 % of CD45+ cells; SMAKO NMD: 0.94 ± 0.52 vs. SMAKO HFD: 2.24 ± 0.40 % of CD45+ cells; pint=0.63, pdiet=0.02*, pgenotype=0.01*) and CD8+ T cells (control NMD: 0.49 ± 0.10 vs. control HFD: 2.02 ± 0.59 % of CD45+ cells; SMAKO NMD: 0.12 ± 0.07 vs. SMAKO HFD: 0.52 ± 0.07 % of CD45+ cells; pint=0.20, pdiet=0.04*, pgenotype=0.04*) that was significantly attenuated in SMAKO mice. In addition, HFD fed control mice had a greater reduction in eosinophils compared to NMD floxed control. The reduction in eosinophils was attenuated in SMAKO (control NMD: 5.28 ± 2.01 vs. control HFD: 1.28 ± 0.07 % of CD45+ cells; SMAKO NMD: 5.92 ± 0.94 vs. SMAKO HFD: 4.49 ± 1.60 % of CD45+ cells; pint=0.42, pdiet=0.09, pgenotype=0.23). These data suggest that ET-1-induced adipose tissue inflammation in obese mice occurs via activation of ETAR on VSMCs. R01DK124437, P30GM149404, and T32HL105324. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Deciphering visceral adipose tissue regulatory T cells: Key contributors to metabolic health.

Regulatory T cells (Tregs) within the visceral adipose tissue (VAT) play a crucial role in controlling tissue inflammation and maintaining metabolic health. VAT Tregs display a unique transcriptional profile and T cell receptor (TCR) repertoire, and closely interact with adipocytes, stromal cells, and other immune components within the local VAT microenvironment. However, in the context of obesity, there is a notable decline in VAT Tregs, resulting in heightened VAT inflammation and insulin resistance. A comprehensive understanding of the biology of VAT Tregs is essential for the development of Treg-based therapies for mitigating obesity-associated metabolic diseases. Recent advancements in lineage tracing tools, genetic mouse models, and various single cell "omics" techniques have significantly progressed our understandings of the origin, differentiation, and regulation of this unique VAT Treg population at steady state and during obesity. The identification of VAT-Treg precursor cells in the secondary lymphoid organs has also provided important insights into the timing, location, and mechanisms through which VAT Tregs acquire their distinctive phenotype that enables them to function within a lipid-rich microenvironment. In this review, we highlight key recent breakthroughs in the VAT-Treg field while discussing pivotal questions that remain unanswered.

The thrombin receptor PAR4 supports visceral adipose tissue inflammation.

Thrombin inhibition suppresses adiposity, WAT inflammation and metabolic dysfunction in mice. Protease-activated receptor (PAR)1 does not account for thrombin-driven obesity, so we explored the culprit role of PAR4 in this context. Male WT and PAR-4-/- mice received a high fat diet (HFD) for 8 weeks, WT controls received standard chow. Body fat was quantified by NMR. Epididymal WAT was assessed by histology, immunohistochemistry, qPCR and lipase activity assay. 3T3-L1 preadipocytes were differentiated ± thrombin, acutely stimulated ± PAR4 activating peptide (AP) and assessed by immunoblot, qPCR and U937 monocyte adhesion. Epicardial adipose tissue (EAT) from obese and lean patients was assessed by immunoblot. PAR4 was upregulated in mouse WAT under HFD. PAR4-/- mice developed less visceral adiposity and glucose intolerance under HFD, featuring smaller adipocytes, fewer macrophages and lower expression of adipogenic (leptin, PPARγ) and pro-inflammatory genes (CCL2, IL-1β) in WAT. HFD-modified activity and expression of lipases or perilipin were unaffected by PAR4 deletion. 3T3-L1 adipocytes differentiated with thrombin retained Ki67 expression, further upregulated IL-1β and CCL2 and were more adhesive for monocytes. In mature adipocytes, PAR4-AP increased phosphorylated ERK1/2 and AKT, upregulated Ki67, CCl2, IL-β and hyaluronan synthase 1 but not TNF-α mRNA, and augmented hyaluronidase-sensitive monocyte adhesion. Obese human EAT expressed more PAR4, CD68 and CD54 than lean EAT. PAR4 upregulated in obesity supports adipocyte hypertrophy, WAT expansion and thrombo-inflammation. The emerging PAR4 antagonists provide a therapeutic perspective in this context beyond their canonical antiplatelet action.

Two regulatory T cell populations in the visceral adipose tissue shape systemic metabolism.

Visceral adipose tissue (VAT) is an energy store and endocrine organ critical for metabolic homeostasis. Regulatory T (Treg) cells restrain inflammation to preserve VAT homeostasis and glucose tolerance. Here, we show that the VAT harbors two distinct Treg cell populations: prototypical serum stimulation 2-positive (ST2+) Treg cells that are enriched in males and a previously uncharacterized population of C-X-C motif chemokine receptor 3-positive (CXCR3+) Treg cells that are enriched in females. We show that the transcription factors GATA-binding protein 3 and peroxisome proliferator-activated receptor-γ, together with the cytokine interleukin-33, promote the differentiation of ST2+ VAT Treg cells but repress CXCR3+ Treg cells. Conversely, the differentiation of CXCR3+ Treg cells is mediated by the cytokine interferon-γ and the transcription factor T-bet, which also antagonize ST2+ Treg cells. Finally, we demonstrate that ST2+ Treg cells preserve glucose homeostasis, whereas CXCR3+ Treg cells restrain inflammation in lean VAT and prevent glucose intolerance under high-fat diet conditions. Overall, this study defines two molecularly and developmentally distinct VAT Treg cell types with unique context- and sex-specific functions.

Zinc Transporter ZnT1 mRNA Expression Is Negatively Associated with Leptin Serum Concentrations but Is not Associated with Insulin Resistance or Inflammatory Markers in Visceral Adipose Tissue.

The aim of this study was to evaluate the relationship between biomarkers of chronic inflammation, insulin resistance, and zinc transporter ZnT1 expression in human visceral adipose tissue. Visceral adipose tissue obtained from 47 adults undergoing laparoscopic surgery for cholecystectomy was used to analyze ZnT1 mRNA expression by RT-qPCR. ZnT1 mRNA levels were compared between subjects with normal weight, overweight, and obesity. A significantly lower ZnT1 expression was observed in overweight and obesity compared with normal-weight subjects (p = 0.0016). Moreover, subjects with normal weight had significantly higher serum zinc concentration (97.7 ± 13.1mg/L) than subjects with overweight (87.0 ± 12.8mg/L) and obesity (83.1 ± 6.6mg/L) (p = 0.002). Pearson test showed a positive correlation between serum zinc concentrations and ZnT1 mRNA expression in visceral adipose tissue (r = 0.323; p = 0.031) and a negative correlation with body mass index (r = - 0.358; p = 0.013). A linear regression model was used to analyze the associations between ZnT1 mRNA expression and serum zinc levels, insulin resistance (HOMA2-IR), serum adipokines (leptin and adiponectin), and serum inflammation biomarkers (tumor necrosis factor alpha, interleukin-6, and C-reactive protein). Interestingly, leptin concentrations were negatively associated with ZnT1 mRNA expression (p = 0.012); however, no significant associations were found for the rest of the analyzed variables. Future research is needed to analyze the causality of negative association between ZntT1 expression in visceral adipose tissue and leptin.

Inhibition of visceral adipose tissue-derived pathogenic signals by activation of adenosine A2AR improves hepatic and cardiac dysfunction of NASH mice.

A2AR-disrupted mice is characterized by severe systemic and visceral adipose tissue (VAT) inflammation. Increasing adenosine cyclase (AC), cAMP, and protein kinase A (PKA) formation through A2AR activation suppress systemic/VAT inflammation in obese mice. This study explores the effects of 4 wk A2AR agonist PSB0777 treatment on the VAT-driven pathogenic signals in hepatic and cardiac dysfunction of nonalcoholic steatohepatitis (NASH) obese mice. Among NASH mice with cardiac dysfunction, simultaneous decrease in the A2AR, AC, cAMP, and PKA levels were observed in VAT, liver, and heart. PSB0777 treatment significantly restores AC, cAMP, PKA, and hormone-sensitive lipase (HSL) levels, decreased SREBP-1/FASN, MCP-1, and CD68 levels, reduces infiltrated CD11b+ F4/80+ cells and adipogenesis in VAT of NASH + PSB0777 mice. The changes in VAT were accompanied by the suppression of hepatic and cardiac lipogenic/inflammatory/injury/apoptotic/fibrotic markers, the normalization of cardiac contractile [sarco/endoplasmic reticulum Ca2+ ATPase (SERCA2)] marker, and cardiac dysfunction. The in vitro approach revealed that conditioned media (CM) of VAT of NASH mice (CMnash) trigger palmitic acid (PA)-like lipotoxic (lipogenic/inflammatory/apoptotic/fibrotic) effects in AML-12 and H9c2 cell systems. Significantly, A2AR agonist pretreatment-related normalization of A2AR-AC-cAMP-PKA levels was associated with the attenuation of CMnash-related upregulation of lipotoxic markers and the normalization of lipolytic (AML-12 cells) or contractile (H9C2 cells) marker/contraction. The in vivo and in vitro experiments revealed that A2AR agonists are potential agent to inhibit the effects of VAT inflammation-driven pathogenic signals on the hepatic and cardiac lipogenesis, inflammation, injury, apoptosis, fibrosis, hypocontractility, and subsequently improve hepatic and cardiac dysfunction in NASH mice.NEW & NOTEWORTHY Protective role of adenosine A2AR receptor (A2AR) and AC-cAMP-PKA signaling against nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH) possibly via its actions on adipocytes is well known in the past decade. Thus, this study evaluates pharmacological activities of A2AR agonist PSB0777, which has already demonstrated to treat NASH. In this study, the inhibition of visceral adipose tissue-derived pathogenic signals by activation of adenosine A2AR with A2AR agonist PSB0777 improves the hepatic and cardiac dysfunction of high-fat diet (HFD)-induced NASH mice.

Metabolic activity of visceral adipose tissue is associated with age-related macular degeneration: a pilot 18F-FDG PET/CT study.

Obesity is known to increase the risk and severity of age-related macular degeneration (AMD). Increased inflamed metabolic activity of visceral adipose tissue (VAT) is considered as a crucial underlying mechanism for the harmful effects of obesity. In this study, we aimed to investigate the inflamed metabolic activity of VAT with 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and their association with AMD. A total of 57 elderly participants (aged ≥ 50 years) who underwent 18F-FDG PET/CT for health screening and subsequent fundoscopic exam for complaint of recently impaired vision were enrolled. The metabolic activity of VAT was measured from the maximum standardized uptake value (SUVmax) of VAT. The early AMD participant was defined as the participant with either eye satisfying AMD and without any sign of advanced AMD (neovascular AMD or geographic atrophy). The late AMD participant was defined as the participant with either eye satisfying advanced AMD. VAT SUVmax was highest in participants with late AMD, intermediate in early AMD, and lowest in non-AMD participants. The levels of systemic inflammation surrogate markers were also highest in late AMD group. Furthermore, VAT SUVmax was positively correlated with systemic inflammation surrogate markers and independently associated with the late AMD. The metabolic activity of VAT evaluated by 18F-FDG PET/CT was associated with the severity of AMD and synchronized with the level of systemic inflammation. Thus, VAT SUVmax could be potentially employed as a surrogate marker of obesity-driven VAT inflammation associated with AMD.

Reduced Lipopolysaccharide-Binding Protein (LBP) Levels Are Associated with Non-Alcoholic Fatty Liver Disease (NAFLD) and Adipose Inflammation in Human Obesity.

Lipopolysaccharide (LPS) and its binding protein LBP have emerged as potential contributors to the progression from overweight/obesity to overt metabolic diseases and NAFLD. While LPS is known to activate hepatocyte inflammation, thus contributing toward NAFLD development, the role of LBP is more intricate, and recent data have shown that experimental reduction in hepatic LBP promotes NAFLD progression. In this cross-sectional investigation, we evaluated circulating LBP in relation to obesity, NAFLD, visceral adipose tissue (VAT) inflammation, and type 2 diabetes (T2D). We recruited 186 individuals (M/F: 81/105; age: 47 ± 10.4 years; BMI: 35.5 ± 8.6 kg/m2); a subgroup (n = 81) underwent bariatric surgery with intra-operative VAT and liver biopsies. LBP levels were higher in obese individuals than non-obese individuals but were inversely correlated with the parameters of glucose metabolism. Reduced LBP predicted T2D independent of age, sex, and BMI (p < 0.001). LBP levels decreased across more severe stages of hepatosteatosis and lobular inflammation, and were inversely associated with VAT inflammation signatures. In conclusion, LBP levels are increased in obese individuals and are associated with a more favorable metabolic profile and lower NAFLD/NASH prevalence. A possible explanation for these findings is that hepatic LBP production may be triggered by chronic caloric excess and facilitate LPS degradation in the liver, thus protecting these individuals from the metabolic consequences of obesity.

Abstract B101: Obesity mediates altered triple-negative breast cancer tumor biology in African American women independent of ancestry

Abstract African American (AA) breast cancer (BC) is associated with a higher incidence of aggressive BC phenotypes at younger age, higher grade of tumor as compared to BCs of age-matched patients of European American (EA). For AA women, there is a higher frequency of the more aggressive TNBC subtype and of the PAM50-molecular basal subtype. AA tumors are enriched for inflammatory and immune pathways, implicating inherited susceptibility associated with African ancestry. Obesity induces a state of low-grade inflammation. AA women tend to be more obese than EA and have elevated a inflammatory markers, including CRP, IL6, and IL1. Since inflammation related to obesity is a reflection of dysfunctional adipocyte biology, we used dataset GSE88837 to perform in silico analysis of gene expression changes in visceral adipose tissue for AAs and EAs. AA adipose tissue is more inflamed than EAs at the same level of obesity (BMI&amp;gt;30). There was a high expression of secreted mediators causing systemic inflammation, including heat shock protein 60 (HSPD1), CXCL1, S100A9, and SPP1. VEGFA, S100A9, and SPP, tumor-promoting angiogenic mediators, were higher in obese AAs than EAs. These data indicate that obesity enhances inflammation in visceral adipose tissue of AAs. We performed in silico analysis of dataset GSE78958, of 400 BC patients annotated for race, BMI, and hormone receptor expression. We analyzed BC patients for differential gene expression, PAM50 subtype, tumor stage and grade, based on race and BMI. AA women have a higher BMI (48.9%) than EA women (32.3%) and a higher percentage of poorly differentiated tumors (51.1%) than EAs (40.6%). AA women with BMI &amp;gt;30, had more basal-like tumors (34.8%) than EA women (19.3%). These analyses confirm that excess adiposity promotes the basal BC phenotype. With BMI &amp;gt;30 as a criterion for obesity, the GSE78958 dataset containing BCs for 96 AA and 200 EA patients was analyzed for differences in gene expression. DEGs showed upregulation of T cell exhaustion marker PTPN22 and LAIR2. The metastasis and proliferation promoting chemokines CXCL1, CCL2, CXC12, CXCR4, and S100A9 were higher in the BCs of obese AAs, than BCs of non-obese AAs. Stemness related genes, STAT1, SOX4, and KLF4, were higher in BCs of obese AAs. CD163-expressing M2 macrophages were higher in BCs of obese AAs. Our group showed that there was a considerable overlap of genes among African and AA cases, but there were some non-overlapping genes indicating that ancestry alone cannot explain the genetic diversity in the tumor phenotype of AA patients. The divergence was largely driven by an upregulated gene signature found among AAs and not seen among African patients. GSE78958 (obesity BC dataset) was mapped for ancestral correlation of altered genes in the AA BC dataset. Ancestry mapping showed an inverse correlation of HSPD1 with ancestry. Obesity upregulated HSPD1 in BCs of AAs as well as in AA adipose tissue and decreased the probability of survival for women of AA ethnicity, suggesting delineation of ancestry-specific and race-specific effects. Citation Format: Deepa Bedi, Rachel Martini, Melissa B. Davis, Clayton Yates. Obesity mediates altered triple-negative breast cancer tumor biology in African American women independent of ancestry [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr B101.

N1-methylnicotinamide impairs gestational glucose tolerance in mice.

N1-methylnicotinamide (MNAM), a product of methylation of nicotinamide through nicotinamide N-methyltransferase, displays antidiabetic effects in male rodents. This study aimed to evaluate the ameliorative potential of MNAM on glucose metabolism in a gestational diabetes mellitus (GDM) model. C57BL/6N mice were fed with a high-fat diet (HFD) for 6 weeks before pregnancy and throughout gestation to establish the GDM model. Pregnant mice were treated with 0.3% or 1% MNAM during gestation. MNAM supplementation in CHOW diet and HFD both impaired glucose tolerance at gestational day 14.5 without changes in insulin tolerance. However, MNAM supplementation reduced hepatic lipid accumulation as well as mass and inflammation in visceral adipose tissue. MNAM treatment decreased GLUT4 mRNA and protein expression in skeletal muscle, where NAD+ salvage synthesis and antioxidant defenses were dampened. The NAD+/sirtuin system was enhanced in liver, which subsequently boosted hepatic gluconeogenesis. GLUT1 protein was diminished in placenta by MNAM. In addition, weight of placenta, fetus weight, and litter size were not affected by MNAM treatment. The decreased GLUT4 in skeletal muscle, boosted hepatic gluconeogenesis and dampened GLUT1 in placenta jointly contribute to the impairment of glucose tolerance tests by MNAM. Our data provide evidence for the careful usage of MNAM in treatment of GDM.

Extracellular inflammasome particles promote visceral adipose tissue inflammation

Abstract Background The metabolic syndrome is characterized by a chronic low-grade inflammation that increases the risk for cardiovascular events. With its capability to activate IL-1β, the NLRP3-inflammasome is believed to affect the inflammatory process. When the inflammasome is primed and activated, cytosolic ASC aggregates into the ASC-speck. This inflammasome particle can persist in the extracellular space after the cell it originated from underwent pyroptosis. Purpose We aimed to assess the role of extracellular inflammasome particles as a potential target to reduce chronic inflammation in the metabolic syndrome. Methods Male C57BL6/J mice received either a chow or high-fat-diet (HFD) for 7, 14 or 21 weeks. Flow cytometry and fluorescence microscopy were used to detect inflammasome particles. Adipocytes and stromal vascular fraction (SVF) were isolated from subcutaneous (scWAT) and visceral white adipose tissue (vWAT) using collagenase. Results Mice subjected to HFD show increased NLRP3-inflammasome priming in the SVF of visceral but not subcutaneous WAT (vWAT: 4-fold p&amp;lt;0.001, scWAT: 1-fold). The frequency of ASC-specks induced by the NLRP3-activating agent nigericin correlates with immune cell infiltration (macrophages: r=0.83) and disruption of metabolic homeostasis (bodyweight: r=0.8). Co-staining of nigericin-induced ASC-specks with CD45 and CD11b suggests their derivation from myeloid cells of the SVF. ASC-speck formation can be fully inhibited with the NLRP3-specific inhibitor MCC950. Adipocytes likely do not form ASC-specks as they, despite upregulating the required genes when primed with lipopolysaccharide (e.g. IL-1β: 8-fold), fail to activate the inflammasome in-vitro. In chow-fed mice, cells carrying cytosolic ASC are evenly dispersed in the WAT and can be co-stained with the macrophage marker F4/80. When a metabolic syndrome is acquired, ASC-positive cells form crown-like-structures around dying adipocytes in which ASC-speck formation takes place. In the vWAT of HFD-fed mice, we found ASC-specks that were externalized and also taken up by adipocytes. Co-culture of isolated ASC-specks with adipocytes induced ER-stress and resulted in upregulation of IL-6 (42-fold), CCL2 and TNFα after 24h. In addition, previously undifferentiated bone marrow derived macrophages internalized these particles, which lead to a pro-inflammatory shift. Finally, also human endothelial cells responded to isolated ASC-specks with upregulation of the leukocyte adhesion molecules VCAM1 and ICAM1. Conclusion Our study suggests that extracellular inflammasome particles accumulate in metabolically altered visceral adipose tissue and contribute to a pro-inflammatory environment. The imbalance between pro- and anti-inflammatory immune response is an important contributor to the development of cardiovascular disease. Extracellular inflammasome particles could be an interesting target for novel therapeutic approaches to reduce chronic inflammation.

Gestational Weight Gain Is Associated with the Expression of Genes Involved in Inflammation in Maternal Visceral Adipose Tissue and Offspring Anthropometric Measures

Background: Adequate gestational weight gain (GWG) is essential for maternal and fetal health. GWG may be a sign of higher visceral adipose tissue (VAT) accretion. A higher proportion of VAT is associated with an inflammatory process that may play a role in the fetal programming of obesity. This study aimed to (1) compare the expression of genes involved in inflammatory responses (TLR2, TLR4, NFκB, IKKβ, IL-1RA, IL-1β, IL-6, IL-10, TNF-α) in the VAT of pregnant women according to GWG and (2) explore whether VAT inflammation and GWG are related to offspring anthropometric measures. Material and methods: 50 women scheduled for cesarean section who delivered term infants were included in the study. We collected maternal omental VAT, and the expression of genes was examined with RT-qPCR. Results: Women with excessive and with adequate GWG had significantly higher expressions of most inflammatory genes than women with insufficient GWG. Neonates from mothers with excessive GWG had greater birth weight and chest circumference than those from mothers with insufficient GWG. GWG was positively correlated with fetal birth weight. Conclusions: The VAT expression of most genes associated with inflammatory pathways was higher in excessive and adequate GWG than in pregnant women with insufficient GWG. Moreover, GWG was found to be positively associated with newborn weight.

Four-and-a-Half LIM-Domain Protein 2 (FHL2) Induces Neuropeptide Y (NPY) in Macrophages in Visceral Adipose Tissue and Promotes Diet-Induced Obesity.

Obesity is characterized by the expansion of the adipose tissue, usually accompanied by inflammation, with a prominent role of macrophages infiltrating the visceral adipose tissue (VAT). This chronic inflammation is a major driver of obesity-associated comorbidities. Four-and-a-half LIM-domain protein 2 (FHL2) is a multifunctional adaptor protein that is involved in the regulation of various biological functions and the maintenance of the homeostasis of different tissues. In this study, we aimed to gain new insights into the expression and functional role of FHL2 in VAT in diet-induced obesity. We found enhanced FHL2 expression in the VAT of mice with Western-type diet (WTD)-induced obesity and obese humans and identified macrophages as the cellular source of enhanced FHL2 expression in VAT. In mice with FHL2 deficiency (FHL2KO), WTD feeding resulted in reduced body weight gain paralleled by enhanced energy expenditure and uncoupling protein 1 (UCP1) expression, indicative of activated thermogenesis. In human VAT, FHL2 was inversely correlated with UCP1 expression. Furthermore, macrophage infiltration and the expression of the chemokine MCP-1, a known promotor of macrophage accumulation, was significantly reduced in WTD-fed FHL2KO mice compared with wild-type (wt) littermates. While FHL2 depletion did not affect the differentiation or lipid metabolism of adipocytes in vitro, FHL2 depletion in macrophages resulted in reduced expressions of MCP-1 and the neuropeptide Y (NPY). Furthermore, WTD-fed FHL2KO mice showed reduced NPY expression in VAT compared with wt littermates, and NPY expression was enhanced in VAT resident macrophages of obese individuals. Stimulation with recombinant NPY induced not only UCP1 expression and lipid accumulation but also MCP-1 expression in adipocytes. Collectively, these findings indicate that FHL2 is a positive regulator of NPY and MCP-1 expression in macrophages and herewith closely linked to the mechanism of obesity-associated lipid accumulation and inflammation in VAT. Thus, FHL2 appears as a potential novel target to interfere with the macrophage-adipocyte crosstalk in VAT for treating obesity and related metabolic disorders.

Immune profile of adipose tissue from youth with obesity and asthma.

Obesity is a risk factor for paediatric asthma. Obesity-mediated systemic inflammation correlates with metabolic dysregulation; both are associated with asthma burden. However, adipose tissue inflammation is not defined in obesity-related asthma. Define adipose tissue inflammation and its association with metabolic measures in paediatric obesity-related asthma. Cellular profile of stromal vascular fraction from visceral adipose tissue (VAT) from youth with obesity-related asthma (n = 14) and obesity without asthma (n = 23) was analyzed using flow cytometry and correlated with metabolic measures. Compared to youth without asthma, VAT from youth with obesity-related asthma was enriched for leukocytes and macrophages, including M1 and dual M1M2 cells, but did not differ for CD4+ lymphocytes, and endothelial cells, their progenitors, and preadipocytes. M1 macrophage counts positively correlated with glucose, while M1M2 cells, CD4+ lymphocytes, and their subsets negatively correlated with high-density lipoprotein, in youth with obesity without asthma, but not among those with obesity-related asthma. Enrichment of macrophage-mediated inflammation in VAT from youth with obesity-related asthma supports its role in systemic inflammation linked with asthma morbidity. Lack of correlation of VAT cells with metabolic dysregulation in youth with obesity-related asthma identifies a need to define distinguishing factors associated with VAT inflammation in obesity-related asthma.

Circulating miRNAs Detect High vs Low Visceral Adipose Tissue Inflammation in Patients Living With Obesity.

The severity of visceral adipose tissue (VAT) inflammation in individuals with obesity is thought to signify obesity subphenotype(s) associated with higher cardiometabolic risk. Yet, this tissue is not accessible for direct sampling in the nonsurgical patient. We hypothesized that circulating miRNAs (circ-miRs) could serve as biomarkers to distinguish human obesity subgroups with high or low extent of VAT inflammation. Discovery and validation cohorts of patients living with obesity undergoing bariatric surgery (n = 35 and 51, respectively) were included. VAT inflammation was classified into low/high based on an expression score derived from the messenger RNA levels of TNFA, IL6, and CCL2 (determined by reverse transcription polymerase chain reaction). Differentially expressed circ-miRs were identified, and their discriminative power to detect low/high VAT inflammation was assessed by receiver operating characteristic-area under the curve (ROC-AUC) analysis. Fifty three out of 263 circ-miRs (20%) were associated with high-VAT inflammation according to Mann-Whitney analysis in the discovery cohort. Of those, 12 (12/53 = 23%) were differentially expressed according to Deseq2, and 6 significantly discriminated between high- and low-VAT inflammation with ROC-AUC greater than 0.8. Of the resulting 5 circ-miRs that were differentially abundant in all 3 statistical approaches, 3 were unaffected by hemolysis and validated in an independent cohort. Circ-miRs 181b-5p, 1306-3p, and 3138 combined with homeostatic model assessment of insulin resistance (HOMA-IR) exhibited ROC-AUC of 0.951 (95% CI, 0.865-1) and 0.808 (95% CI, 0.654-0.963) in the discovery and validation cohorts, respectively, providing strong discriminative power between participants with low- vs high-VAT inflammation. Predicted target genes of these miRNAs are enriched in pathways of insulin and inflammatory signaling, circadian entrainment, and cellular senescence. Circ-miRs that identify patients with low- vs high-VAT inflammation constitute a putative tool to improve personalized care of patients with obesity.

Butyrate prevents visceral adipose tissue inflammation and metabolic alterations in a Friedreich’s ataxia mouse model

Friedreich's ataxia (FA) is a neurodegenerative disease resulting from a mutation in the FXN gene, leading to mitochondrial frataxin deficiency. FA patients exhibit increased visceral adiposity, inflammation, and heightened diabetes risk, negatively affecting prognosis. We investigated visceral white adipose tissue (vWAT) in a murine model (KIKO) to understand its role in FA-related metabolic complications. RNA-seq analysis revealed altered expression of inflammation, angiogenesis, and fibrosis genes. Diabetes-like traits, including larger adipocytes, immune cell infiltration, and increased lactate production, were observed in vWAT. FXN downregulation in cultured adipocytes mirrored vWAT diabetes-like features, showing metabolic shifts toward glycolysis and lactate production. Metagenomic analysis indicated a reduction in fecal butyrate-producing bacteria, known to exert antidiabetic effects. A butyrate-enriched diet restrained vWAT abnormalities and mitigated diabetes features in KIKO mice. Our work emphasizes the role of vWAT in FA-related metabolic issues and suggests butyrate as a safe and promising adjunct for FA management.

Mitochondrial sourcing of interferogenic ligands and an autoantigen in human obesity-associated metaflammation.

Visceral adipose tissue (VAT) inflammation contributes to metabolic dysregulation in obesity. VAT recruitment and activation of plasmacytoid dendritic cells (pDCs) through toll-like receptor 9 (TLR9) recognition of self-DNA, leading to induction of type I interferons, arecrucial innate triggers for this VAT inflammation. It was hypothesized that mitochondrial DNA (mtDNA) can contribute to TLR9 activation in VAT-recruited pDCs in obesity, and this study aimed to identify the carrier protein for ligand access to TLR9 and to explorewhether this also provides for a source of autoantigensin this context. VAT samples, used for gene expression studies as well as adipose explant cultures, were collected from patients with obesity (n = 54) and lean patients (n = 10). Supernatants from human pDC cultures, treated with adipose explant culture supernatants, were used for interferon α ELISA. Venous plasma, from patients with (n = 114) and without (n = 45) obesity, was used for an ELISA for autoantibodies. MtDNA from VAT in obesity, in complex with mitochondrial transcription factor A protein (TFAM), acts as interferogenic ligands for pDCs. Humoral autoreactivity against TFAM is also induced in obesity. Interferogenic ligands and an autoantigen can be sourced from dysfunctional mitochondria in VAT of humans with obesity. Further therapeutic and prognostic potential for this immune mechanism in obesity warrants exploration.

Differential effects of plant and animal fats on obesity-induced dyslipidemia and atherosclerosis in Ldlr-/-.Leiden mice.

Cardiovascular disease (CVD) is closely associated with obesity through risk factors such as dyslipidemia and chronic low-grade inflammation, which may be affected by diet. Dietary fats have been extensively studied in relation to CVD risk, however these studies have not always yielded consistent results, most likely due to lack in control of experimental conditions and confounding factors. Here we studied the effects of different plant and animal fats on dyslipidemia, inflammation, and atherosclerosis. Ldlr-/-.Leiden mice were fed isocaloric energy-dense diets with translational macronutrient composition for 28 weeks. The diets were identical apart from the type of fat they contained: either (1) a mixture of olive and rapeseed oil, (2) sunflower oil, (3) pork fat, (4) beef fat, or (5) milk fat. The fatty acid composition of the diets was determined and effects on circulating lipid and inflammatory risk factors and atherosclerosis were examined, complemented by adipose tissue histology and liver transcriptomics. While visceral fat mass, adipocyte size, and adipose tissue inflammation were not differentially affected by the diets, atherosclerotic lesion load and severity was more pronounced with increasing dietary saturated fatty acid content and decreasing monounsaturated and polyunsaturated fatty acid content, and hence most pronounced with beef and milk fat. These differential effects were accompanied by increases in pro-atherogenic plasma lipids/lipoproteins (e.g., triglycerides, apolipoprotein B), activation of pro-atherogenic cytokine/chemokine signaling pathways in liver, and with circulating pro-atherogenic mediators of inflammation altogether providing a rationale for the differential effects of plant and animal fats.

1702-P: Altered Gene Expression Signatures following COVID-19 Infections and/or mRNA Vaccination in Human Adipose Tissue

Obesity is associated with an increase in morbidity and mortality from Coronavirus disease- 2019 (COVID-19). Adipose tissue (AT) demonstrates high expression of angiotensin-converting enzyme 2 (ACE2), a host cell entry factor of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 has been shown to infect AT, where it continues to proliferate, thereby contributing to local inflammation. Since visceral AT inflammation may play a role in the pathogenesis of type 2 diabetes, we investigated the molecular and histological AT signatures after a Covid-19 infection and/or mRNA vaccination. We investigated 54 paired subcutaneous (SC) and visceral adipose tissue (VAT) biopsies from the Leipzig Obesity BioBank in subgroups based on positive versus negative SARS-CoV-2 infection as well as mRNA vaccination status in comparison to BMI and age matched controls obtained before appearance of Covid-19 (N=27). We compared gene expression signatures by RNA-Sequencing analyses, morphology changes in AT as well as circulating inflammation markers across the groups. In relation to a Covid-19 infection, we find a distinct gene expression signature and morphology in AT suggesting that SARS-CoV-2 affects AT and may mediate the disease course. In this context, inflammation of AT, but also an altered secretion profile from AT could link obesity to its metabolic complications, but also to long Covid-19 disease courses. Disclosure S.Krupka: None. M.Blüher: Advisory Panel; Boehringer Ingelheim Inc., Lilly, Novo Nordisk, Consultant; Novo Nordisk Foundation, Speaker's Bureau; Amgen Inc., AstraZeneca, Bayer Inc., Daiichi Sankyo, Novartis, Sanofi-Aventis Deutschland GmbH. N.Klöting: None.